I've been using PostBuilder (used to be called gramspacer) for several months now and I use it almost every single work day. PostBuilder makes it super convenient for organizing and planning content for my Instagram pages and the founder is very responsive if you have questions or if there's ever an issue. I definitely recommend them!
Instaspacer - Putting the spaces back into Instagram
Subtitle Edit - Free subtitle editor with visual sync, time adjustments etc.Subtitle Edit Online · Subtitle Edit Videos · Subtitle Edit 3.
PicMerger - Merge photos side by side, create beautiful photo collages, customize your content with built-in photo editing tools, and more
Aegisub - Aegisub is a free, cross-platform open source tool for creating and modifying subtitles. Aegisub makes it quick and easy to time subtitles to audio, and features many powerful tools for styling them, including a built-in real-time video preview.
StoriesStudio App - StoriesStudio allows you to take a long video and cut it down into separate clips that can then be uploaded to Instagram stories, WhatsApp, TikTok, and more.
Time Adjuster - It's Windows application that can: Make your subtitles to appear earlier or later. Convert your subtitle files into other formats. SYNCHRONIZE text with video VERY EASY ! Join & split subtitle files.